DESCRIPTION: The aim of this research is the development of a bacterial host/vector system for the expression of heterologous membrane proteins. The unusual properties of the bacterium Rhodospirillum rubrum will be exploited for this purpose. This organism forms an intracytoplasmic membrane (ICM) that is not essential for growth. While mutants that do not make major membrane proteins do not form ICM, they retain the capacity to do so. Over expression of a membrane protein in such a mutant should result in production of ICM containing the overexpressed proteins. Because the ICM can be readily isolated, protein purification should be facilitated. Use of R. rubrum in this application will require development of an expression vector. For this purpose, an R. rubrum membrane protein will be used as a reporter for expression. Heterologous proteins will then be expressed in R. rubrum mutants using the newly developed expression vector. Ultimately this host/expression system should be useful for many eukaryotic proteins, including those of human origin as well as those of pathogens. This will have important applications in basic biomedical research. Over expression of proteins that naturally occur in low abundance is necessary for structural studies including X-ray crystallography. Analysis of proteins encoded by open reading frames identified by sequencing of partial or complete genomes will be facilitated by expression in this bacterial host/vector system. Finally, this system has potential for production of materials including vaccines.